Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in CPP):

Solution:
// D - Grid Repainting
#include <bits/stdc++.h>
using namespace std;
using vi = vector<int>;
using vvi = vector<vi>;
using VC = vector<char>;
using VVC = vector<VC>;
using PII = pair<int,int>;
#define rp(i,s,e) for(int i=(s);i<(e);++i)
#define rpz(i,e) rp(i,0,e)

int bfs(int H, int W, VVC &S){
	int dx[4]={0,-1,0,1}, dy[4]={-1,0,1,0};
	vvi dist(H+1, vi(W+1, -1));
	dist[1][1] = 0;
	S[1][1] = '_';
	queue<PII> q;
	q.push({1, 1});
	while(!q.empty()){
		int i,j; tie(i,j)= q.front(); q.pop();
		rpz(k, 4){
			int y = i + dy[k], x = j + dx[k];
			if(S[y][x] != '.') continue;
			dist[y][x] = dist[i][j] + 1;
			q.push({y, x});
			S[y][x] = '_';
		}
	}
	return dist[H][W];
}

int main(){
	int H,W; cin>>H>>W;
	VVC S(H+2,VC(W+2, '#'));
	int white = 0;
	rpz(i, H){
		string s; cin>>s;
		rpz(j, W){
			if(s[j] == '.') white++;
			S[i+1][j+1] = s[j];
		}
	}
	int dist = bfs(H, W, S);
	cout<< (dist<0? -1: white - dist - 1) <<endl;
}